Almost all of the league's elite defenses have a distinctly unique identity. New England thrives in aggressive man coverage. San Francisco is a proponent of wide-9 defensive ends with their talent-loaded front four, held together in the middle by an elite cover linebacker in Fred Warner. Baltimore, despite a questionable run defense, is one of the best units in the league because of how well they keep offenses guessing with their endless array of creative coverages and fluid fronts.
The Pittsburgh Steelers, perhaps quietly, are among that elite group with their own flare. The third-ranked overall defense and fourth-ranked pass defense per DVOA, the Steelers' identity can be attributed to how they send pressures and manipulate the middle of the field with their safeties, particularly from two-deep safety shells.
To dive even further into the niche of their identity, the Steelers like sending their nickel (or apex, depending on the formation) defender, often from the wide side of the field. Since they play out of two-high shells quite often anyway, it's not difficult for them to sprinkle in blitzes from the slot area while still having a defender over the top to cap the slot receiver. This is especially true against teams that like condensed formations, such as the Rams and Cardinals. Capping the receiver directly can be a bit of a tell that a blitz is coming, but with how effectively the Steelers mix up coverages and how talented their safeties are, they can often execute well enough regardless.
Here is a simple example of Pittsburgh blitzing the nickel from the field against Arizona last week. The Steelers come out in a two-high shell with their front set away from the strength of the offense (under). Since Arizona has their passing strength to the field in a tight formation, Pittsburgh can cheat their safeties over toward the passing strength, allowing safety Terrell Edmunds (34) to comfortably sit over the slot receiver at about 10 yards. When the ball is snapped and slot corner Mike Hilton (28) fires off toward the quarterback, Edmunds is already in position to cap the slot receiver vertically and buy enough time for the blitz to get home.
The Colts spread out their passing strength into the field in this clip, but the same principle applies for the Steelers defense. The safety (Edmunds, 34) walks over to cap the slot receiver while the nickel cornerback (Hilton, 28) fires off the snap to blitz. By the time backup quarterback Brian Hoyer gets to the top of his dropback after the play fake, there is a blitzing nickelback diving at his feet while his slot receiver is getting squeezed down on over the middle.
The nickelback is not always the one to get sent on the blitz, though. Be it a game plan-specific decision or an adjustment to the offense shifting around the formation, Pittsburgh has shown they will blitz whoever is in the "apex" position over/near the slot receiver.
Before the Bengals send a receiver in motion, the Steelers don't look to be gearing up for a blitz on the boundary side of the field. Both safeties appear to be lining up 12 to 14 yards deep while the nickelback (Hilton, 28) is a few yards off instead of up at the line of scrimmage as if he were to blitz. It's not until Cincinnati shifts the second player from trips (the middle receiver) to the opposite side of the field that one of Pittsburgh's safeties walks closer to cap the slot receiver. Now free safety Minkah Fitzpatrick (39) is 7 yards inside and over the slot receiver, while linebacker Mark Barron (26) is free to blitz away from the strength of the defensive front, just like the Steelers were doing in the previous two clips. Bengals quarterback Ryan Finley doesn't catch the adjustment and gets ripped down by Barron flying unblocked off the edge.
The Steelers also switch it up every now and again to keep opposing offenses off their scent. Whether it's sending different players or not sending any at all, Pittsburgh does a good job of mixing in a few different calls into these same blitz looks.
The Steelers are set up similarly in this example as they were in the previous example. However, the blitz comes from the short side of the field this time, though it's still away from the strength of the front. Pittsburgh has a safety and linebacker both sitting over the slot receiver, with the safety about 7 yards deep. As Browns quarterback Baker Mayfield gets ready to call for the snap, Edmunds creeps up to blitz through the B-gap (between guard and tackle) while edge rusher T.J. Watt takes a wide path around the offensive tackle. Barron locks into the inside hip of the slot receiver and locks him out from being able to bend to the middle of the field. As the coverage on the other side of the field holds up, Watt is able to beat his man around the edge and bring down Mayfield for a sack.
These all seem like minor tweaks, but the Steelers sent a different position, from a different side of the field, through a different gap than they usually do. That's a ton of change for the offense to take in, even if it looks the same on the surface.
This time, the Steelers don't send anybody after posturing as if they were going to send the nickelback again. Instead of blitzing, Pittsburgh looks to drop into a Cover-3 look with a late deep rotation from Fitzpatrick (39) on the weak side. With the assumed blitzer coming from the strong side, Rams quarterback Jared Goff likely assumed he would have more room to work with on that side of the field than he ended up getting. Goff freezes up trying to determine where receivers are going to open up in between zones and is forced to check down to running back Todd Gurley, whom he somehow misses by a noticeable margin.
The last clip also speaks to another key pillar in Pittsburgh's defense: safety rotations. Fitzpatrick is one of the smartest safeties in the league and a quality athlete to boot, and Edmunds is among the best athletes at the position. The Steelers can get away with rotating these two all around the field before and at the snap because of how well they can move around and track moving pieces at the same time.
This looks to be the same coverage in two separate weeks against the Browns. In both clips, the Steelers come out in a two-high look with six defensive backs across the board. The weak nickel (bottom of the screen in both cases) starts to bail to a deep middle position just before the snap, splitting the two deep safeties on his way there. The two deep safeties then walk down to become hook defenders, while the strong nickel and the middle linebacker fan out to become curl/flat defenders. Whether you want to call it a variation of Tampa-2 or Cover-3 does not much matter to me because it functions the same way. In fact, Mayfield even gets hung up looking at the same area of the field in both clips because of the strong safety dropping into the hook area.
This scheme ends up covering all the same areas as that in the previous clip, but the rotation itself is a bit different. Rather than dropping both safeties to become hook defenders while the weak nickel becomes a deep-middle player, the Steelers push their weak safety to an outside deep-third while their weak outside cornerback sits in the flat (cloud coverage). The weak nickel (Cameron Sutton, 20) rotating up then becomes part of a triangle rotation with the field safety and the middle linebacker. The weak nickel slides up to replace the field safety deep, the field safety slides down to become the strong hook, and the linebacker slides over from the middle to play the weak hook. All the moving pieces get Mayfield to believe the slot receiver breaking over the middle will be open because the linebacker slides away, but Fitzpatrick flies down and jumps inside of the route for a pass breakup.
Again, call it Tampa-2. Call it rotating to Cover-3 cloud. Diante Lee, a high school coach in San Diego, calls it 2 Slice, which he says is true Tampa-2 on one side and Inverted-2 on the other. The point is that Pittsburgh is able to manipulate the entire middle of the field -- everything between the painted numbers -- because of what their safeties are capable of, particularly Fitzpatrick.
So long as Pittsburgh's secondary stays healthy, especially Fitzpatrick and Edmunds, they will be able to ride these tactics out for the rest of the season. It's hard to imagine Josh Allen or Sam Darnold, whom the Steelers face over the next two weeks, will be the ones to crack the code. Lamar Jackson may be able to get the best of them in the regular season finale, but even Jackson already struggled against the Steelers pass defense in Week 5. Pittsburgh still has to win all these games in spite of their quarterback situation, but the pass defense will be able to hold up its end of the bargain to keep this unlikely season afloat.